7548 | Chem. Soc. Rev., 2014, 43, 7548--7561 This journal is © The Royal Society of Chemistry 2014 Cite this: Chem. Soc. Rev., 2014, 43, 7548 Zeolites as catalysts in oil refining Ana Primo* a and Hermenegildo Garcia* ab Oil is nowadays the main energy source and this prevalent position most probably will continue in the next decades. This situation is largely due to the degree of maturity that has been achieved in oil refining and petrochemistry as a consequence of the large effort in research and innovation. The remarkable efficiency of oil refining is largely based on the use of zeolites as catalysts. The use of zeolites as catalysts in refining and petrochemistry has been considered as one of the major accomplishments in the chemistry of the XXth century. In this tutorial review, the introductory part describes the main features of zeolites in connection with their use as solid acids. The main body of the review describes important refining processes in which zeolites are used including light naphtha isomerization, olefin alkylation, reforming, cracking and hydrocracking. The final section contains our view on future developments in the field such as the increase in the quality of the transportation fuels and the coprocessing of increasing percentage of biofuels together with oil streams. This review is intended to provide the rudiments of zeolite science applied to refining catalysis. Key learning points  Role of zeolites in the most important oil refining processes.  Nature of Bro ¨nsted and acid sites in zeolites.  Relationship between structure and composition of zeolites and catalytic activity.  Bifunctional acid and hydrogenation catalysts based on zeolites.  Major general trends in oil refining. Introduction Modern societies require extensive consumption of energy that nowadays is predominantly based on the combustion of fossil fuels provided by refining. 1–3 From the point of view of Sustainability and Environment protection, currently there is much interest in repla- cing as a primary energy resource fossil fuels by alternative renew- able energy sources. 4 However, considering the degree of maturity and efficiency in the use of oil and the difficulty in developing on a massive scale other energy sources, it is very likely that the prevalence of refining and petrochemistry will continue in the next decades, particularly considering the new oil fields found and modern extraction technologies that recover more exhaustively hydrocarbons from bituminous sand and unconventional sources. 5,6 The current efficiency of refining and petrochemistry is largely based on the use of highly active, selective and durable catalysts, 7,8 zeolites being the paradigmatic example of solid acids and large surface area supports for developing environmentally benign processes. 8 This outstanding level of development in refin- ing and petrochemistry has been achieved over the years by a combination of intensive research and innovation. The purpose of this tutorial review is to summarize the prevalence in refining of catalytic processes based on the use of zeolites. We will start with a brief description of the composition, structure and properties of zeolites with a focus on their application as solid catalysts. The main part of this review will be the description of some catalytic processes, such as paraffin isomerization, isobutene–butene alkylation, reforming, cracking and hydrocracking, currently per- formed in the refining industry to produce massive amounts of fuels and lesser quantities of chemicals. In the final part, we will provide our view on future developments in the field, particularly, the quest for even more efficient zeolites and co-processing of biofuels. Zeolites: composition, structure and synthesis Zeolites can be defined as crystalline, porous aluminosilicates in which the primary building blocks are TO 4 tetrahedra having a Si 4+ or Al 3+ cation (T atoms) at the center and four oxygen a Instituto de Tecnologı ´a Quı ´mica CSIC-UPV, Univ. Politecnica de Valencia, Av. De los naranjos s/n, 46022 Valencia, Spain. E-mail: aprimoar@itq.upv.es, hgarcia@qim.upv.es b Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia Received 1st November 2013 DOI: 10.1039/c3cs60394f www.rsc.org/csr Chem Soc Rev TUTORIAL REVIEW Published on 27 March 2014. Downloaded on 15/12/2015 15:00:58. View Article Online View Journal | View Issue